Pneumatic tool



Feb. 23, 1932; F. H. THOMAS PNEUMATIC TOOL Filed Oct. 22, 1928 INVENTOR.

Flqy HT]: 027103 4%; Hi5 ATTORNEY Patented Feb. 23, 1932 UNITED STATES PATENT OFFICE FLOYD H. THOMAS, F MILAN, PENNSYLVANIA, ASSIGNOR TO INGERSOLL-RAND COM- PANY, 0F JERSEY CITY, NEW JERSEY, A CORPORATION OFNEW JERSEY PNEUMATIC TOOL Application filed. October 22, 1928. Serial No. 314,130.

i the invention, showing the position of the movable parts when the piston is in its rearward position, and

Figure 2 is a view similar to Figure 1 showing the position of the movable Parts when 2 the piston is at the end of its working stroke.

Referring more particularly to the drawings in which similar characters refer to similar parts in both views, A designates a cylinder of a pneumatic tool having a reciprocatory piston B mounted therein and adapted to deliver blows of impact to a working implement C. The working implement G extends slidably through a bushing D which forms a closure for the front end of the cylinder A. A back cylinder washer E forms a closure for the rearward end of the cylinder and a handle portion F is mounted thereon. The cylinder A, the back cylinder washer E and the handle portion F may be rigidly secured together by the usual side bolt construction (not shown) or any other suitable means. A valve chest G formed partly in the handle portion F and partly in the back cylinder washer E is provided with a plate valve H which is adapted to oscillate in a valve chamber J. A pin K passing through the valve and into the rear cylinder washer E holds the valve H in place while permitting oscillation of the valve. It should be understood that the invention is not confined to the use of the specific valve disclosed as the valve selected is shown merely for the purpose of illustration.

Pressure fluid is admitted to the valve chamber J through a fluid pressure supply passage L controlled as usual by a throttle valve (not shown). The valve H controls in let passages O and P. The inlet passage 0 leads from the valve chamber J to the rearward end of the cylinder A to deliver pres sure fluid to that end of the cylinder for throwing the piston forwardly to deliver its working stroke. The inlet passage P connects with a continuation P in the wall of the cylinder A and leading to the forward end of the cylinder.

Near the extreme forward end of the cylinder an inlet port Q, of smaller cross sectional area than the passage P affords communication between the said passage and the 5 cylinder A. Located rearwardly of this small inlet port Q, and forwardly of an exhaust port R is a second inlet port S leading from the inlet passage P into the cylinder A. As illustrated in the drawings the inlet port S is of considerably greater cross sectional area than the inlet port Q. However, it should be clear'that a port of different size may be substituted for the port S and the mechanism will continue to operate but under certain conditions variation in the relative size of the ports S and Q may be found necessary. For operation under ordinary conditions the port S may be of the same cross sectional area as the passage P.

The operation of the device is as follows: Assuming the piston to bein the position shown in Figure 1 and pressure fluid being admitted to the valve chamber J, the pressure fluid will pass over the raised end of the valve H and through the inlet passage 0 into the rearward end of the cylinder A throwing the piston B forwardly to strike the working implement C. When the exhaust port R is closed or covered by the piston B, the piston will begin to compress the air in the forward end of the cylinder A and in the inlet passages P and P, the air thus position shown in Figure 2 and the rearward end of the cylinder has exhausted to a pressure substantially equal to atmospheric pressure through the exhaust port B. Live pressure fluid enters the forward end of the cylinder through the small port Q and moves the piston B rearwardly. When the piston has moved rearwardly far enough to uncover the inlet port S, the live pressure fluid supply reaching the forward end of the cylinder is suddenly augmented by a greater supply of pressure fluid entering through the port S. This fresh supply of pressure fluid throws the piston B sharply to the rear compressing air in the rearward end of the cylinder, thus causing the valve H to be thrown due to the pressure fluid built up in the rearward end of the cylinder which exerts an upward force against the left hand v end of the valve H which is assisted by the sudden expansion of air in the inlet passage P due tothe opening of the port S. The cycle of operations just completed is continued indefinitely at the will of the operator.

It will be readily seen by any one skilled in the art that economy in operation results from driving the piston B backward through V the major portion of its return stroke by admitting just sufficient air to the front end 'of the cylinder through the small port Q to move the piston with sufficient rapidity so as not to interfere with the speed of opera- 7 tion of the tool. However, as it is not necessary to have the piston strike a heavy blow on its return stroke, it is not necessary to supply air so rapidly on the return stroke as V on the working stroke and thus the object sought is accomplished.

It will be clear from the mode of operation described above that as the piston makes the major portion of its return stroke under the influence of a restricted flow of pressure fluid, the force of the upward stroke of the piston is not as great as it would be if the piston were impelled by an unrestricted flow of pressure fluid. This easing of the blow of the piston on its return stroke has been found to greatly reduce vibration which is of great advantage to the operator and prolongs the life of the tool.

I claim:

1. In a percussive tool, the combination of a cylinder and a piston, a valve chest having a valve chamber, inlet passages leading from the valve chamber to the cylinder, a valve in the valve chamber controlling the inlet passages, a free exhaust port in the cylinder, and a plurality of ports spaced with respect to each other along the lengthof the cylinder forwardly of the exhaust port and affording communication between the cylinder and one of the inlet passages to admit successive charges of pressure fluid into the cylinder for actuating the piston rearwardsectional'area to restrict the flow of ly, one of said ports being of smaller area than the said inlet passage.

2. In a percussive tool, the combination of a cylinder and a piston, a valve chest having a valve chamber, inlet passages leading from the valve chamber to the cylinder, a valve in the valve chamber controlling the inlet passages, a free exhaust port in the cylinder, an inlet port of relatively small cross pressure fluid into the forward end of the cylinder leading from one of the inlet passages, and a second inlet port located rearwardly of said inlet port of smaller cross sectional area and forwardly of the exhaust port, said second inlet port leading from the same inlet passage as the first said inlet port to the forward end of the cylinder to assure a faster supply of pressure fluid to the forward end of said cylinder when the piston has completed part of the return stroke.

3, In arpercussive tool, the combination of a cylinder and a hammer piston in the cylinder, said cylinder having an exhaust port, a valve chest having a valve chamber, a distributing valve in said valve chamber, a rear ward inlet passage leading from the valve chamber to the rearward end of the cylinder, a front inlet passage leading from the valve chamber to the forward end of the cyl--- ,cated forwardly of said exhaust port and rearwardly of the small inlet port and adapted to be covered by the piston during a substantial part of the rearward stroke of said i piston.

- In testimony whereof I have signed this specification.

FLOYD H. THOMAS.

CERTIFICATE OF CORRECTION.

Patent No. 1,846,372. Granted February 23, 1932, to

FLOYD H. THOMAS.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, line 79, claim 2, for the word "smaller read greater; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 22nd day of March, A. D. 1932.

M. J. Moore,

(Seal) Acting Commissioner of Patents. 

